International Collaboration in Infectious Disease Research on Lassa fever (Lassa ICIDR) Project 1: Evaluation of 2nd generation recombinant assays as point-of-care diagnostics and surveillance tools for Lassa fever. Much of what is known about Lassa fever was elucidated in specialized isolation units in endemic areas and represents the most severe clinical manifestations of disease. Studies have shown that treatment with ribavirin is effective at controlling viremia in acute Lassa fever patients but is most effective when administered early in disease progression. However, onset of Lassa fever is gradual and nonspecific, making the disease difficult to recognize. Patients presenting with early signs of Lassa fever are nearly impossible to distinguish from other febrile diseases, such as malaria and typhoid, based on clinical findings alone. Patients are more likely to visit a peripheral health unit (PHU) during the early stages of disease, when clinical signs and symptoms of Lassa fever are nonspecific. These PHUs have limited laboratory capacity and personnel. Febrile patients are commonly administered antimalarial and antibiotic drugs and sent home, only to return days later with more severe disease. It can be several days after onset of symptoms and after no response from antibiotics that clinicians consider Lassa fever at which point patients are referred to the specialized units that can diagnose and treat Lassa fever patients. Over 75% of patients presenting to the Kenema Government Hospital (KGH) Lassa Ward had symptoms for over 7 days. The delay in treatment likely attributes to the 69% case fatality rate in LASV antigenemic cases seen at the Lassa Ward. We hypothesize that building diagnostic capacity for Lassa fever at PHUs will enable community health workers to diagnose and refer suspected Lassa fever cases earlier, and as a result, are more likely to consider and screen for Lassa fever when febrile patients present to their PHUs. This will enable us to learn more about the early stages of disease. Specific Aim 1 is to evaluate deployment of next-generation Lassa fever recombinant antigen immunodiagnostics for point-of-care detection in peripheral health units. Specific Aim 2 is to determine feasibility of using reLASV diagnostics as an epidemiological tool for country-wide seroprevalence studies. Specific Aim 3 is to utilize recombinant LASV diagnostics to define correlates of immunity to Lassa fever in patient contacts with little or no disease thereby identifying resistance patterns and susceptible cohorts for Lassa fever. Specific Aim 4 is to develop the data collection and data management capacity at the Kenema Government Hospital (KGH).